Ion etching of amorphous and semicrystalline fibres

Ion etching of amorphous and semicrystalline fibres produces structures which can be observed in either the transmission electron microscope or the scanning electron microscope. The structures so produced have previously been identified as resulting from the etching process (artifacts), or as representing characteristics of the material, or both. The artifacts can be eliminated or minimized by rotating the sample during irradiation, using a low angle of incidence, and ensuring that the temperature of the sample surface remains low. When such precautions are used, amorphous fibres and semicrystalline fibres which are not oriented remain featureless after ion etching. Oriented semicrystalline fibres, however, develop a striated structure which is oriented perpendicular to the stretch direction. The spacing between the striations is in the range of 500 to 5000 å, an order of magnitude larger than the characteristic lamellar spacing in the materials. These transverse structural features reflect characteristic features of drawn fibres; but the relation between these features and the lamellar spacing is unclear.